1. Field of the Invention
The present invention relates to novel curable polythioether compositions which include reactive liquid polythioether components which react with each other rapidly and at room temperature to form an elastomer having terminal groups which chemically bond to metallic surfaces such as aluminum alloy and aluminum composite surfaces, and/or to epoxy primer coatings applied to such surfaces. Such compositions are well suited for use as protective coatings or in caulks for filling gaps, cracks or other narrow spaces in metallic, polymeric, composite and/or epoxy, polyurethane, or acrylic-primed surfaces since they are light in weight, they bond to such surfaces during rapid curing at room temperatures, they provide improved filler properties over a wide range of temperatures, and they form smooth rubbery deposits having excellent water resistance and corrosion resistance, expansion-and-contraction properties and resistance to cracking.
2. Discussion of the Known Art
Reference is made to commonly-owned U.S. Pat. No. 5,206,285 relating to water-base coating compositions containing a hydrolyzable silane polymer precursor formed by reacting an epoxy trialkoxy silane with a primary amino trialkoxy silane for 24 hours at room temperature. The precursor solution is hydrolyzed and cured in situ, such as on an aluminum surface, to react the terminal silanol sites of the polymer with the aluminum surface during curing to form a strongly bonded coating or filler.
Reference is also made to U.S. Pat. Nos. 4,366,307 and 4,960,844 which disclose polythioether coating and caulking compositions in which the polythioether is a liquid polymer which is curable at room temperature to form an elastomer having terminal vulcanizable or reactive groups such as silyl, hydroxy, alkoxy, mercapto and/or other reactive groups. The compositions of the Patent can contain amounts of filler, such as carbon-black, and are disclosed for use as water-, solvent-, fuel- and temperature-resistant sealants.
Reference is also made to U.S. Pat. No. 4,786,667 which discloses curable liquid polyether polymers having hydrolyzable silyl end groups, formed by reacting epoxy-substituted hydrolyzable silane monomers, diepoxy polyoxyalkylenes and aromatic diamines. The polymers of the Patent require the use of a curing catalyst such as an organo tin compound.
Various other polythioether liquid polymers are known which are curable by heating for 24 hours or more at room temperatures to form rubbery solids which can contain fillers as colorants, conductivity particles, etc. While such compositions display better adhesive properties for metallic surfaces and better resistance to cracking than other coating, gap-filling or caulking compositions, such as those based upon polyurethanes, silicone sealing polymers or other conventional binder materials used in coating, caulking and gap-filling compositions, they present problems with respect to their relatively slow curing properties and/or their requirement for the inclusion of curing catalysts. Also they are not reactive with metallic surfaces for chemical-bonding thereto.